The uptake of glucocerebrosidase is dramatically improved by exposing mannose residues in the oligosaccharide side chain of the glycoprotein. This strategy enables enzyme infusions as a therapeutic tool. The GCRC supported clinical studies are aimed at determining the lowest doses of enzyme needed to be effective treatment. It is becoming clear that response to enzyme replacement must be individualized. In order to evaluate the lowest effective dose, it is important to collect data on clinical responses to enzyme replacement therapy over the next five years.